Potentiometer



March 10, 1964 MELLOR 3,124,777

POTENTIQMETER Filed Sept. 13, 1961 I 11/1 Ill/ 1111 ,5, 5 am 4.5 2a 24 INVENTOR.

Arrow/5y 4 United States Patent 3,124,777 PQTENTIOMETER Robert H. Mellor, Reseda, Calif. (7109 Slryview Drive, Riverside, Calif.) Filed Sept. 13, 1961, Ser. No. 137,811 16 Claims. (Cl. 338174) This invention relates to a potentiometer and more particularly to an adjustable potentiometer in which the electrical portion of the device is separated from the mechanical portion thereof and sealed therefrom.

Although adjustable potentiometers have been designed and produced in the past, the instant invention provides a new and improved adjustable potentiometer which is more accurately adjustable and capable of retaining such adjustment throughout extreme shock and vibration conditions. The potentiometer of this invention is particularly adaptable for miniature construction but is equally adaptable for use with potentiometers of varying sizes. The potentiometer features a construction in which the electrical portion of the potentiometer is isolated from the mechanical portion and is more completely moistureproofed and seal-proofed from the mechanical portion so as to prevent entrance of moisture thereto and/or of foreign particles such as minute particles ground off of moving mechanical parts during extensive use of the potentiometer.

The invention further features more complete moisture proofing portions of the potentiometer from the exterior of the casing thereof, more reliable electrical connections and a more constant vibration free wiper contact due to the particular construction of the wiper means of the invention which enables the use of a substantially shorter spring arm contact with the resistance element thereof.

It is therefore an object of this inventionto provide a new and improved adjustable potentiometer in which the electrical portion thereof is physically isolated from the mechanical portion thereof and sealed therefrom to seal against humidity and foreign particles.

Another object of this invention is to provide a new and improved adjustable potentiometer which incorporates improved wiper means capable of more sustained electrical contact with a resistance element and which decreases dis turbances and breaking of a circuit due to vibrations or shock conditions.

A further object of this invention is to provide a new and improved adjustable potentiometer which provides an improved gear ratio between the manual operable actuating and the electrical portions of the potentiometer.

A still further object of this invention is to provide a new and improved adjustable potentiometer which incorporates a simplified assembly of electrical and mechanical parts in which all of the electrical parts are assembled together in one section thereof and the mechanical parts in another section, the sections being isolated from each other in more complete sealed relationship.

Still a further object of this invention is to provide a new and improved adjustable potentiometer in which the wiper means may be selectively and readily pre-set in rotated relationship relative to the mechanical operating means thereof.

Another object of this invention is to provide a new and improved adjustable potentiometer in which the adjustment may be effectively operated from the exterior of the casing to facilitate adjustment thereof.

An object of this invention is to provide a new and improved adjustable potentiometer which is economical to manufacture, is relatively light in weight, can be adapted to potentiometers of varying sizes, from sub-miniature potentiometers to potentiometers of conventional size, and is capable of mass production.

A general object of this invention is to provide a new and improved adjustable potentiometer of the character described which overcomes disadvantages of prior means and methods heretofore intended to accomplish generally similar purposes.

These and other objects of this invention will be more apparent from the following drawings, detailed description and appended claims.

In the drawings:

FIGURE 1 is a top plan view of the potentiometer of this invention, with a top cover thereof removed for greater clarity;

FIGURE 2 is a vertical cross-sectional view as taken substantially along the lines 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary, horizontal, cross-sectional view as taken substantially along the lines 33, with parts shown in elevation; and

FIGURE 4 is a perspective view, in elevation, illustrating parts thereof in exposed relationship.

Referring in detail to the drawings, there is shown by way of illustration, but not of limitation, a potentiometer designed and constructed in accordance with this invention and generally designated by the numeral 10. The potentiometer it) includes a casing 11, preferably of nonelectrical conductive material such as plastics or the like. The casing is preferably substantially square in configuration so as to facilitate edge-to-edge installation thereof in respect to similar otentiometers so as to be more compact in installation. A pair of mounting holes 12 are preferably provided extending through the casing 11 and through a relatively-flat top wall 13 and a relatively-fiat bottom wall 14 secured to the casing through which bolts, screws or the like may be passed for securing the casing 11 to a suitable foundation in either single or multiple, stacked relationship. An upper recess 16 and a lower recess 17 are provided in the casing 11, the recesses being joined by a substantially central bore 18 communicating therebetween. The recess 16 is preferably cylindrical in configuration to seat a C-shaped resistance element 19 in an annular gnoove 21 formed in the bottom 22 of the recess and adjacent to the periphery thereof. The recess 17 is preferably functionally configurated to enclose a worm gear 23 and a worm 24 having its teeth meshed with the teeth of the gear 23 as will be hereinafter described.

The recess 16 contains essentially the electrical parts of the potentiometer whereas the recess 17 houses the movable mechanical parts thereof. The cavity 16 is sealed from the exterior by a suitable gasket 26 sandwiched between the top Wall 13 and an upper top edge 27 of the casing 11 whereas the lower recess 17 is sealed from the exterior by a similar gasket 23 placed between the bottom wall 14 and a lower face 2? of the casing 11 so as to effectively seal both recesses 16 and 17 from the exterior. The gasket 26 is preferably of a laminated construction,

including an inner layer of non-corrosive material, such as a non-metallic material of plastics, such as Mylar, adhesively bonded to the top 13 and the upper surface 27 with a thermosetting or thermoplastic adhesive material compatable to both surfaces. The gasket 28 may be of similar construction to adhesively bind the bottom 14 to the lower casing surface 29.

The Worm 24 includes worm teeth 31 extending into the recess 17 and meshed with the teeth 32 of the gear 23 and includes an extension 33 extending outwardly of the casing 11 as through a bore 34, the extension 33 being sealed from the exterior by suitable means such as an O-ring sealing member 36. The extension 33 at the portion extending outwardly of the casing 11 is preferably kerfed as at 37 so that the worm 24 may be conveniently rotated from the exterior as by a screw driver or the like. In this manner, the worm gear 23 is rotated within the casing 11 by rotating the worm 24 selectively in selective directions from the exterior of the casing 11.

The worm gear 23 is provided with a circular or annular recess 38 to receive a depending annular bearing 39 formed on the casing wall 41 formed between the recesses 16 and 17 so as to surround an upstanding shaft 42 secured to or, as illustrated, formed integrally with the gear 23. The shaft 42 extends through the bore 18 and into the recess 16. The shaft 42 is appreciably reduced in diametrical dimension relative to the bore 18 so as to define an annular space 43 between the shaft 42 and the bore 18 in which an annular sealing member 44 resides, the sealing member 44 forming an effective seal between the shaft and the bore 18 to seal the recess 16 from the recess 17.

An enlarged head member 46 has an axial bore 47 tightly fitting the upper end of the shaft 42 to which it is affixed as by cementing, or the like. The head member 46 includes an annular skirt 45 surrounding the shaft 42 and extending into the bore 18 as best seen in FIGURE 2, the bottom of which is spaced from the annular recess 38 formed in the gear 23 to house the O-ring seal 44. The head member 46 further includes an annular flange 48 adjacent to its upper end which, as best seen in FIG- URES 2 and 4, is provided with a plurality of equally circumferentially spaced radial grooves 49 on its under side. The head member 46 is preferably made of a nonelectrical conductor material.

The resistance element 19 seated in the groove 21 is broadly C-shaped in configuration, having a core 51 which is substantially circular with the exception of a gap 52 separating adjacent ends thereof and is formed of nonconductive material with an electrical conductor wire 53 wrapped therearound. One end 54 of the wire 53 is electrically connected, as by welding or the like, to a terminal 56 having an end housed in a recess 57 of the casing 11 and extending through an aperture 58 of the casing to the exterior of the casing to form a terminal 59 adapted to be connected to an electrical circuit (not shown) providing electrical energy to the Wire 53. The opposite end 61 of the wire 53 is similarly secured to an inner end 62 of a terminal spaced from the terminal end 56 and similarly housed in the recess 57. The terminal 62 extends through an aperture 63 of the casing 11 to form an external terminal 64 adapted to be similarly electrically connected to the electrical circuit. The apertures 58 and 63 are preferably sealed from the exterior by a thermo-setting or thermo-plastic material such as epoxy or the like. A third terminal designated by the numeral 66 extends through a transverse aperture 67 of the casing 11 and has an internal end 68 residing in a transverse groove of the bottom of the recess 16 for electrical connection as by spot welding, soldering or the like to an annular terminal member 69 seated on the bottom 22 of the recess 16 and surrounding the annular skirt 45 of the head member 46 and in spaced relationship to the underside of the flange 48 of the head.

A wiper means, generally designated by the numeral 71 and best seen in FIGURES 2 and 4, is rotatably supported in the upper recess 16 and drivingly, yieldably, engaged with the shaft 42 for rotative movement in response to rotation of the shaft. The Wiper means 71 includes an annular body 72 of electrical conductive material having a central opening 73 through which the annular skirt 45 of the head 46 extends. The body 72 has a resilient characteristic and includes an offset end 74 having a depending dimple 76 in sliding contact with the annular terminal 69. The body 74 further includes an upwardly offset resilient sliding contact 77 in engagement with the upper periphery of the resistance element ,19 and an upwardly extending projection 78 engageable with a selective groove 49 on the underside of the head flange 48 as will be hereinafter described. The inherent resiliency of the wiper means 71 biases the projection 78 into one of the grooves 49, the depending dimple 76 into engagement with the annular terminal 69 and the sliding 4 contact 77 into a sliding engagement with the wire 53 of the element 19.

As will now be more fully understood from the foregoing description, rotation of the worm gear 24 by means of engagement therewith with a screw driver, coin, or the like with the kerf 37, the worm gear 23 is rotated in one direction to rotate the shaft 42 and the head 46 secured thereto in the same direction. By virtue of the engagement of the protrusion 78 with a selective groove 49, rotation of the head 4-6 is transmitted to the annular wiper means 71 to vary the position of the sliding contact '77 relative to the resistance element 19. Rotation of the worm gear 23 in an opposite direction causes an opposite movement of the sliding contact 77 relative to the resistance element 19 in like manner.

As best seen in FIGURES 1 and 2, a stop member in the form of a web 79 is positioned in the gap 52 of the resistance element 19 and is abuttable by the sliding contact 76 when the contact is rotated into a position wherein it contacts the zero resistance of the resistance element 19. The web 79 may be integrally formed with the casing 11 and extending radially inward into the recess 16 or may be optionally suitably secured thereto by suitable means, but is preferably formed of a nonelectrical conductive material. When the sliding contact 77 is in abutment with the web 79 in the zero resistance position, continued rotation of the shaft 42 by means of the worm 24 to rotate the worm gear 23, the protrusion 78 is yieldably biased or cammed outwardly of a groove 49 by virtue of its sloped walls 81, to permit further rotation of the head 46 and shaft 42 while the wiper means 71 is held in abutment with the web 79 and to resiliently snap into the next adjacent radial groove 49 subsequently positioned in line with the projection 78. If desired, the shaft 42 and head 46 may be further rotated to progress the protrusion 78 to ensuing grooves 49 positioned in alignment relative thereto if desired. As a result, the circumferential. distance of the sliding contact 77 may be adjustably and accurately precisely varied relative to the shaft 42 and thereby varied in accordance to the rotated position of the worm 24 from the exterior of the casing without the necessity of opening the casing.

In practice, it has been found advantageous to provide a 25 to 1 gear ratio between gear 23 and the worm 24 and due to the simplicity of the design, and of assembly of the parts wherein all the electrical parts are on one side, the electrical side of the potentiometer and all the mechanical parts being on an opposite side, the mechanical side of the potentiometer, the potentiometer is relatively simple to assembly in spite of the relatively small sizes in which the potentiometer has been produced. As an example, it has been found relatively simple to manufacture a potentiometer having an outer dimension of approximately /2 inch square without sacrificing ease of assembly. In a potentiometer of this size, a core ranging between /6 of an inch to 4, of an inch has'been possible and using a resistance wire ranging between .0004 and .0063 inch. Also, due to the simplicity of installation of the terminals 59, 64 and 66, relatively heavy wire may be used for securement to the relatively thin wire used for the winding on the element 19. p

In potentiometers of relatively small size it is possible to use a friction transmission of rotation between the Wiper means 71 and the shaft 42 to adjust the relativity therebetween. In this event, the grooves 49 and the protrusion 78 may be omitted with the face 72 of the slider being biased into frictional engagement with the underside of the head 46. The spring force created between the portion 74 of the wiper 71 and the sliding contact 77 biases the offset portion 72 into face to face contact with the underside of the head 46 to hold them together until 7 the contact 77 abuts the stop web 79 after which continued rotation of the shaft 42 and 'head 46 causes the ment of this invention, it is recognized that departures may be made therefrom within the scope of this invention which is not limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

What is claimed as new and desired to secure by Letters Patent is:

1. A potentiometer comprising: a casing having an upper recess, a lower recess, a bore communicating between said recesses, a top Wall closing said upper recess in sealed relationship with said casing and a bottom wall closing said lower recess in sealed relationship; a wound wire resistance element mounted in said upper recess; an annular conductive terminal in said upper recess and in insulated relationship relative to said resistance element; resilient conductive wiper means rotatably supported in said upper recess and having a pair of sliding resilient contacts, one of said sliding contacts being engaged with said terminal and another of said contacts being in engagement with said resistance element; said resistance element, said wiper means and said conductive terminal being adapted to be electrically connected through said casing to an electrical circuit; a shaft rotatably mounted in said bore and connected to said wiper means; manually operable means mounted in said lower recess in driving engagement with said shaft and extending outwardly through a side wall of said casing for rotating said wiper means to vary the position of the other of said sliding contacts relative to said resistance element; and an annular sealing means mounted in said bore intermediate said recesses for sealing said shaft and said bore so as to seal said upper recess from said lower recess.

2. A potentiometer as defined in claim 1, including stop means in said upper recess and engageable by said other of said sliding contacts at the zero resistance point of said resistance element and wherein said wiper means is yieldably drivingly engaged with said shaft so as to permit relative movement of said shaft to said wiper means in response to continued rotation of said shaft by said manually operable means when said other of said sliding contacts of said wiper means is in engagement with said stop means.

3. A potentiometer comprising: a casing having an apertured partition forming an upper recess, a lower recess and said aperture placing said upper recess in communication with said lower recess, a top wall closing said upper recess in sealed relationship with said casing and a bottom wall closing said lower recess in sealed relationship; a C-shaped resistance element mounted in said upper recess; an annular conductive terminal supported in said upper recess and substantially co-axial thereto and in insulated relationship to said resistance element; a shaft rotatably mounted in said aperture and extending through said aperture from said lower recess to said upper recess; an annular resilient conductive wiper member mounted in said upper recess and on said shaft for rotation therewith, said wiper member having a first sliding contact engaging said terminal and a second sliding contact engaging said C-shaped resistance element, said resistance element, said wiper member and said terminal being adapted to be electrically connected through a side wall of said casing to an electrical circuit exterior of said casing; manually operable means mounted in said lower recess for selectively rotating said shaft for varying the position of said second sliding contact relative to said resistance element, said means including a gear fixed to said shaft and a worm meshed with said gear and extending through a side wall of said casing for access thereto from the exterior of said casing; and annular sealing means encompassing said shaft in said aperture for sealing said upper recess from said lower recess.

4. A potentiometer as defined in claim 3, including stop means in said upper recess adjacent to a Zero position of said resistance element and intersecting the ends of said resistance element, said stop means being engageable by said second sliding contact at the zero resistance point of said resistance element and wherein said wiper means is yieldably drivingly engaged with said shaft so as to permit relative movement of said shaft to said wiper means in response to continued rotation of said shaft by said manually operable means when said second sliding contact of said wiper means is in engagement with said stop means.

5. A poteniometer as defined in claim 4, including an enlarged head means on said shaft residing in said upper recess and having a plurality of circumferentially spaced radial grooves and a detent on said wiper means and selectively engageable with a selective groove in response to continued rotation of said shaft when said second sliding contact is in engagement with said stop means for predetermining the rotative position of said wiper means relative to said shaft.

6. A potentiometer comprising: a casing having a pair of recesses and a passageway communicating between said recesses and means sealingly closing said recesses from the exterior of the casing: a C-shaped resistance element supported in one of said recesses; an annular conductive terminal mounted in said one of said recesses and in insulated relationship to said resistance element; resilient conductive wiper means rotatably supported in said one of said recesses and having a pair of sliding resilient contacts, one of said sliding contacts being engaged with said terminal and the other of said contacts being engaged with said resistance element, said resistance element, said iwiper means and said conductive terminal being adapted to be electrically connected through said casing to an electrical circuit exteriorly of said casing; manually operable means mounted in the other of said recesses and extending outwardly through a side wall of said casing; motion transmitting means extending through said here and connecting said manually operable means and said wiper means for transmitting motion of said manual ly operable means to vary the position of said other of said sliding contacts relative to said resistance element; and annular sealing means sealing said motion transmitting means relative to said bore so as to seal said one of said recesses from the other.

7. A potentiometer as defined in claim 6, including stop means in said one of said recesses and engagable by said other of said sliding contacts at the zero resistance point of said resistance element and wherein said wiper means is yield-ably drivingly engaged with said motion transmitting means so as to permit relative movement of said motion transmitting means to said wiper means in response to continued operation of said motion transmitting means by said manually operable means when said other of said sliding contacts of said wiper means is in engagement with said stop means.

8. A potentiometer as defined in claim 7, wherein said position of said motion transmitting means relative to said wiper means is adjustable in predetermined increments.

9. A potentiometer comprising:

a casing having an encompassing sidewall, a closed top wall and a closed bottom 'wall;

a partition mounted in said casing intermediate said top wall and said bottom wall for separating said casing into first and second chambers;

a passageway mounted in said partition for placing said first chamber in communication with said second chamber;

a shaft rotatably mounted in said passageway with one end extending into said first chamber and its other end extending into said second chamber;

:a pinion affixed to said other end of said shaft for rotation within said second chamber;

a worm gear rotatably mounted in said second chamher in operative engagement with said pin-ion;

sealing means mounted in said passageway for sealing said first chamber from said second chamber;

an annular conductive terminal encompassing said one end of said shaft in said first chamber;

a C-shaped resistance element encompassing said annular terminal in said first chamber;

an annular resilient conductive Wiper encompassing said one end of said shafit in said first chamber superjacent said annular terminal, said wiper including a depending segment having a detent in sliding contact with said annular terminal and an upwardly, outwardly extending sliding contact engaging said resistance element;

an upstanding protuberance mounted on said Wiper;

a radially grooved head portion rigidly aflixed to said one end of said shaft in such a manner that said grooves are engageable by said upstanding protuberance; and

terminals connected to said Wiper resistance element and said annular terminal for connecting them in an electrical circuit. 10. The potentiometenof claim *9 wherein said sealing means comprises an Oring mounted on said shaft in said 5 passageway.

References Cited in the file of this patent UNITED STATES PATENTS 2,069,440 Hathorn Feb. 2 1937 2,509,058 Haury May 23, 1950 2,632,830 Aust et al. Mar. 24, 1953 2,722,585 Miucher Nov. 1, 1955 2,880,293 Blanca Mar. 31, 1959 2,952,825 Bourns Sept. 13, 1960 2,968,015 1961 Blanco Jan. 10, 

1. A POTENTIOMETER COMPRISING: A CASING HAVING AN UPPER RECESS, A LOWER RECESS, A BORE COMMUNICATING BETWEEN SAID RECESS, A TOP WALL CLOSING SAID UPPER RECESS IN SEALED RELATIONSHIP WITH SAID CASING AND A BOTTOM WALL CLOSING SAID LOWER RECESS IN SEALED RELATIONSHIP; A WOUND WIRE RESISTANCE ELEMENT MOUNTED IN SAID UPPER RECESS; AN ANNULAR CONDUCTIVE TERMINAL IN SAID UPPER RECESS AND IN INSULATED RELATIONSHIP RELATIVE TO SAID RESISTANCE ELEMENT; RESILIENT CONDUCTIVE WIPER MEANS ROTATABLY SUPPORTED IN SAID UPPER RECESS AND HAVING A PAIR OF SLIDING RESILIENT CONTACTS, ONE OF SAID SLIDING CONTACTS BEING ENGAGED WITH SAID TERMINAL AND ANOTHER OF SAID CONTACTS BEING IN ENGAGEMENT WITH SAID RESISTANCE ELEMENT; SAID RESISTANCE ELEMENT, SAID WIPER MEANS AND SAID CONDUCTIVE TERMINAL BEING ADAPTED TO BE ELECTRICALLY CONNECTED THROUGH SAID CASING TO AN ELECTRICAL CIRCUIT; A SHAFT ROTATABLY MOUNTED IN SAID BORE AND CONNECTED TO SAID WIPER MEANS; MANUALLY OPERABLE MEANS MOUNTED IN SAID LOWER RECESS IN DRIVING ENGAGEMENT WITH SAID SHAFT AND EXTENDING OUTWARDLY THROUGH A SIDE WALL OF SAID CASING FOR ROTATING SAID WIPER MEANS TO VARY THE POSITION OF THE OTHER OF SAID SLIDING CONTACTS RELATIVE TO SAID RESISTANCE ELEMENT; AND AN ANNULAR SEALING MEANS MOUNTED IN SAID BORE INTERMEDIATE SAID RECESSES FOR SEALING SAID SHAFT AND SAID BORE SO AS TO SEAL SAID UPPER RECESS FROM SAID LOWER RECESS. 